Methamphetamine (MA) dependence is associated with cognitive impairments that may adversely affect patients' abilities to benefit from treatment. Modafinil is a medication that has been shown to improve cognitive performance in a number of populations, including healthy controls and individuals with attention deficit disorder and schizophrenia. Improving cognitive function in abstinent MA-dependent individuals may enhance their ability to benefit from treatment. Preliminary data suggest that abstinence from MA is associated with excessive daytime sleepiness lasting up to four days. Excessive daytime sleepiness is objectively defined as shortened daytime sleep latency measured using the multiple sleep latency test. Excessive daytime sleepiness may contribute to cognitive impairments in this population. Modafinil treatment has been shown to reduce daytime sleepiness in individuals with sleep disturbances such as narcolepsy and sleep apnea. Modafinil treatment may improve cognitive function and reduce daytime sleepiness in abstinent MA-dependent individuals. The relavance of this proposal to public heath is clear. Methamphetamine abuse and dependence is quickly becoming the major substance abuse issue in the United States. Currently, there are no FDA- approved medications for methamphetamine dependence. As such, cognitive-behavioral therapy is the only empirically validated treatment. Cognitive impairments may render these treatments less effective, and excessive daytime sleepiness may exacerbate cognitive impairments in this population. Improving cognitive function and reducing excessive daytime sleepiness in this population is therefore of paramount importance in treating methamphetamine dependence. [unreadable] [unreadable] [unreadable]